Patents, copyrights, trade marks, and intellectual property
And maybe some other terms I'm not familiar with. Bottom line is, if you design something that is different from everthing else, there is a legal way for you to protect your ownership of the design, at least for a certain period of time.
Any manufacturerer should be able to give you the name of the particular legal process used to protect their interests. Then you need to search out the appropriate govt. registries to find if the magazine you are interested in is listed.
If you seriously intend to manufacture and sell someone else's design, I recommend hiring a legal firm experienced with this sort of thing, and following their advice. It will be money well spent in the long run. There are ways these things can be done.
All else being equal (and it almost never is) bigger bullets tend to work better.